Foaming Characteristics Research Articles

A novel sandwich structured spoof surface plasmon polaritons antenna integrating multibeam and enhanced mechanical performances

The conventional antennas will increase the radar cross section of aircrafts and affect their aerodynamic performances, a novel antenna scheme for radiation and load-bearing integrated design based on composite sandwich structure is proposed. By constructing spoof surface plasmon polaritons (SSPPs) structure and combining it with glass fiber composite (FR-4) plates, the radiation direction of the monopole can be controlled and the antenna will be endowed with load-bearing capacity. At the meantime, polymethacrylimide (PMI) foam is filled in its spacing to improve the mechanical performances greatly. Through electromagnetic (EM) simulation and test, it is found that four-beam radiation in different directions and eight-beam radiation can be realized by changing the position of the FR-4 laminates, and the bandwidth is all about 1 GHz with a peak gain about 6.5 dBi. Out-of-plane compression experiment indicates that the proposed PMI foam-filled multibeam antenna structure (PFMAS) gathers the high load-bearing capacity of multibeam antenna structure (MAS) and the high energy absorption characteristics of PMI foam, showing an obvious coupling effect. Its specific compressive strength is 150.10 % and 6.28 %, and energy absorption capacity per unit volume is 169.91 % and 362.08 % higher than that of PMI foam and MAS, respectively. The proposed PFMAS improves the structural utilization efficiency, and can be applied to some interlocking units of square honeycomb structure to endow multibeam radiation characteristics, which can expand the application of integrated antenna structures effectively.

The expansion and mechanical property-based cavity expansion model for polyurethane grouting underneath the airport pavement

The cavity beneath the pavement will be further expanded by the self-expansion pressure of polyurethane foam after grouting, leading to a decline in its density and mechanical properties of the polyurethane foam. This study proposed a cavity expansion model that coupled the influence of expansion characteristics of polyurethane foam and the mechanical behavior of surrounding soil, thus, the cavity expansion performance with declining expansion pressure and changing mechanical parameters in confined soil and pavement was accurately characterized. The study sequences are as follows: (1) a series of confined expansion tests and uniaxial compression tests were conducted via a self-developed device under various densities and material ratios of the polyurethane foam, thus the prediction formula of expansion pressure with material ratio and density was obtained, and the variation of the ultimate compressive strength and elastic modulus of polyurethane foam can also be quantified; (2) a cavity expansion model considering the decrease of expansion pressure and compressive strength of polyurethane foam during the expansion was proposed based on the combination of the conventional cavity expansion model and the conducted expansion test results; (3) the parametric analysis was conducted to investigate the influence of the initial density (ρ0, refers to the density when the self-expansion pressure starts to apply on the surrounding soil), material ratio of polyurethane foam and the original cavity size on the expansion radius, so the evolution of mechanical properties after cavity expansion under the pavement was revealed based on the density change after expansion (ρ). The feasibility of the improved model for the expansion of polyurethane foam in soil was evaluated in this study, which can provide a reference for the design and optimization of a polyurethane foam filling scheme for the cavity underneath a pavement.

Influence of physical properties and chemical compositions of bitumen on foam characteristics

This study explores the influence of intrinsic bitumen properties on foam characteristics, considering physical properties (penetration, softening point, viscosity), chemical compositions (SARA components, FTIR indices), and physico-chemical characteristics [surface free energy (SFE)]. Ten distinct bitumen samples from two different sources were analyzed. The results reveal that physical properties alone do not sufficiently account for variations in foaming potential among bitumen types. However, chemical compositions and SFE proved to be more informative, explaining the differences in maximum expansion ratio and foam index, specifically for bitumen from the same source. In contrast, when bitumen originates from different sources, none of these intrinsic properties can clarify foaming potential. Notably, intrinsic bitumen properties fail to elucidate the variability in the half-life of foamed bitumen, even when the bitumen types share the same source. These findings underscore the significance of considering multiple factors when assessing bitumen's foam characteristics, particularly when evaluating materials from diverse sources.

Fabrication of granular foam glass aggregates from soda lime silicate glass waste

Granular foam glass aggregates were fabricated from a soda lime silicate glass waste which utilized crude glycerol as a foaming agent and sodium silicate as a binder. The granulation and the foaming process were carried out by a granulator and an electric rotary furnace. The study investigated at first the foaming behavior of different foam glass formulations at various sintering temperatures. Three compositions were formulated which utilized glass powder at 85 wt%, 90 wt%, and 95 wt%, respectively. Sintering was carried out at temperatures from 800℃ to 1200℃ to evaluate for the foaming and melting characteristics. Foam glass with 90% glass powder showed overall uniform pore size distribution and small pores at 800℃ to 900℃ while heating above 1000℃ resulted in sample distortion caused by glass melting and the collapse of foam glass structure. Foam glass composition with 90% glass powder was selected for the fabrication of foam glass granules at the sintering temperatures of 850℃ and 900℃ in rotary furnace. The best result was obtained at 850℃ where the granules did not melt and stick together whereas at 900℃ glass melting on the surface of the foam glass granules occurred significantly.

Effect of egg yolk lipoproteins on foaming properties and interfacial behavior of egg white: Insights into implications for aerated food production

Chicken eggs are often used as an ingredient in oil-containing aerated foods. Different egg yolk lipids have different influence on the foaming properties of egg white, but the exact mechanism behind this influence is not well understood. In this study, we aimed to investigate how high and low-density lipoproteins present in egg yolks impact the macroscopic foam characteristics, rheological properties, and air/water (a/w) interfacial behavior in egg white foams. We found that the addition of low-density lipoprotein (LDL) at a concentration as low as 0.1 % led to a significant decrease in foaming ability (FA) by 284.67–66.67 %. Conversely, high-density lipoproteins (HDL) improved the FA from 284.67 % to 340.67 % within the concentration range of 0.024–0.16 %. Rheological properties showed that the addition of LDL caused a decrease in the viscoelasticity of the interfacial membrane, while HDL had no significant effect on viscoelasticity. Interfacial behavior results suggested that LDL and HDL were detrimental to the diffusion of protein molecules at the a/w interface. This implied that the effects of LDL and HDL on the foaming properties of EWP were mainly due to the competitive adsorption of lipids and proteins at the A/W interface, as well as the interactions between them. This work provides new insights into the effect mechanism of different forms of egg yolk lipids on the foaming properties of egg white, which can be beneficial for regulating oil-containing aerated foods to meet production demands.

Experimental Characterization of a Novel Foam Burner Design for the Low-Excess-Enthalpy Combustion of Very Lean Syngas Mixtures

In the present work, a novel foam burner design is proposed and experimentally evaluated for operation with highly diluted syngas mixtures. The lab-scale burner consists of a purpose-built, square-shaped, high-temperature-grade stainless steel tubular reactor filled with square-sectioned siliconized silico carbide (SiSiC) foams. The assembly was installed in an electrical furnace. Spatially resolved temperature measurements were obtained along the reactor axis, while simultaneous measurements of CO, CO2, H2, O2, and N2 were taken at the burner exit and the water levels were recorded upstream and downstream of the reactor. The results clearly show that flames can be stabilized along the reactor for a range of foam characteristics and operating conditions. Hydrogen conversion efficiencies in excess of 98%, and overall thermal efficiencies close to 95% were achieved for the selected operating conditions. Overall, the denser 10 ppi foam demonstrated superior combustion characteristics in terms of stability, lower enthalpy rises, and a wider operating range at the expense of a very modest pressure drop penalty. Finally, scanning electron microscopy, coupled with energy dispersion spectroscopy (SEM/EDS) and Raman spectroscopy analyses, was used to determine the morphological and compositional characteristics of the pristine and aged foams. After more than 100 h of operation, no significant performance degradation was observed, even though the burner design was subjected to considerable thermal stress.

Effect of pH on Foaming Properties (FC and FS) of Protein Isolates from Two Varieties (DAS & BS) of Nigerian Cultivated Solojo Cowpea (Vigna Unguiculata L. Walp)

Effect of pH on the foaming properties (FC and FS) of protein isolates from two Varieties (DAS & BS) of Nigerian cultivated Solojo cowpea (Vigna Unguiculata L. Walp) was investigated. Results show that the foaming capacity (FC) followed the solubility trend, with a high foaming capacity at pH 2, which slowly reduced between pH 4 - 6 and gradual increase again with pH as the pH approached 10, where it had another high value. As shown in Figures 1-6 noticeable changes in FC were detected as the pH of the protein solution progressed from pH 2 to 10, with minimum foaming capacity at pH 4 in all cases except for DFDAS flour and BS protein isolate (pH 6). The foaming capacity value for 6 h soaked and 48 hr germinated flours, at pH 4 were observed to be greater than at pH 2 and 6. While the maximum was observed in some cases at pH 8 and some pH 10 but FFDAS Raw, 36 and 48 hr; FFBS, 6 hr; DFBS, Raw and 72 hr; BS, 6 and 24 hr germinated, all had their own max values at pH 2. Defatting was also observed to improve the foaming capacity values of all the treatment. The foaming capacity ranged between 15.19 to 121.16%; 44.76 to 127.36%; 31.23 to 110.93%; 30.84 to 121.16%; 64.97 to 210.00%; 62.67 to 222.00% for FFDAS, DFDAS, FFBS, DFBS, DAS, and BS, respectively. The pattern of FC change followed the pH dependent solubility flow of the test material, showing the importance of solubility on foam formation which confirms that solubility of protein has a great influence on the activities of foam also increasing the pH from 4 to 10 improved the foaming characteristics of flour. This observation proved the authenticity that foaming property depends on protein solubility. The foaming capacity of cowpea protein isolates was pH dependent and high at alkaline pH in comparison to acid region.

Dynamic response and residual compressive characteristics of syntactic foams at high and low temperatures

The dynamic response at low and high temperatures and compression after impact of aluminum matrix syntactic foams were studied. There were many cracks in syntactic foams after dynamic compression. The failure behaviors of compression after impact were almost identical to those of quasi-static compression in the late plateau stage and densification stage. The dynamic compressive properties of syntactic foams are greatly affected by the hollow sphere size at low strain rate, but this phenomenon is not remarkable at medium and high strain rates. The compressive strength and plateau stress are insensitive to the strain rate, but the energy absorption increases when increasing the strain rate. The dynamic compressive properties of syntactic foams have low-temperature strengthening and high-temperature softening effects, but the latter no longer changes above 100 ℃. The residual energy absorption is high, which indicates syntactic foams have potential as energy absorbing materials after dynamic damage.

Fire-Retardant Composite Foam with Antioxidant Addition for Prevention and Control of Coal Spontaneous

ABSTRACT Given the shortcomings of existing fire-extinguishing materials, a new type of fire-retarding foam material with composite foaming agents and antioxidants as raw materials was developed. The formula of the composite foaming agent was determined by screening and compounding surfactants. Then, the inhibition characteristics of different antioxidants were tested using a cone calorimeter to determine the best antioxidant. Next, the inhibition characteristics and fire-extinguishing and cooling characteristics of fire-retarding foam were measured by a temperature programmed apparatus and a fire-extinguishing test bench. Results show that the prepared fire-retarding foam achieves the best performance when the mass ratio of the surfactants CAB-35 and MES is 2:3, the mass concentration is 0.4%, and the mass concentration of the tea polyphenols is 1%. In the aspect of low-temperature inhibition, the cross-point temperature of the fire-retarding foam increases from 119.4°C of raw coal to 142.7°C, which is 15.4°C and 6.5°C higher than that of ordinary foam and MgCl2 solution, respectively. At 180°C, the CO concentration is only 1613 ppm, which is about 67.3% of that of raw coal, 78.3% of that of coal treated with ordinary foam, and 85.8% of that of coal treated with MgCl2 solution. The fire-extinguishing times of common foam, MgCl2 solution, and fire-retarding foam are 1780 s, 1350 s, and 820 s, respectively, indicating that fire-retarding foam has the highest fire-extinguishing efficiency.

Enhancement of foaming properties and storage stability of pasteurized liquid egg white through ultrasound modification

Due to the high heat sensitivity of liquid egg white (LEW), there were a loss of foaming properties during pasteurization. At the same time, the temperature of pasteurization was limited by this property and did not limit the growth of microorganisms very well. Therefore, the article hoped to improve the foaming characteristics of pasteurized liquid egg white (PLEW) and to increase the stability during storage by using water-bath ultrasound. It was found that the foaming capacity of the pasteurization only group increased from 270% to 326% under optimal sonication conditions (60 Hz, 400 W, 15 min). The increase in protein solubility and decrease in particle size following ultrasound suggested that ultrasound had a deaggregation effect. The fact that surface tension was reduced suggested that sonication could provide more soluble proteins and a more flexible conformation for PLEW. Both free sulfhydryl and surface hydrophobicity were enhanced, which might be related to the disruption of protein molecular forces by the cavitation effect of ultrasound. The results of spectral analysis again revealed that the essence of ultrasound to improve the foaming properties of PLEW lied in changing the conformation of the protein molecule. Furthermore, the results also demonstrated that the ultrasound-treated LEW showed better foaming properties, minimal changes in viscosity, lower total volatile basic nitrogen content, and a longer shelf life (40 d) during storage. The quality of the ultrasound-treated group remained the most stable. Therefore, ultrasound has great potential for improving the foaming ability and stability of PLEW.

Ultra-durable and high-output triboelectric nanogenerator based on coupling of soft-soft contact and volume effect

Output performance and durability are two key issues for the practical application of triboelectric nanogenerators (TENGs). Although the soft contact structure design is a preferred strategy currently for improving the working life of TENGs, it is difficult to achieve a high output performance. Exploring physical and chemical properties of soft contact materials is a reliable way to achieve ultra-durable and high-output TENGs. Herein, an advanced structure for soft-soft contact is designed by combining ultra-soft PU foam and a spring steel sheet. The soft-soft contact triboelectric nanogenerator (SS-TENG) maintains 100 % of the initial output after 1000,000 operation cycles. More importantly, the high leakage characteristics of PU foam enable the triboelectric charge to migrate up and down inside the dielectric material, significantly improving the output performance of the SS-TENG (charge density and peak power are 144 μC/m−2 and 178 mW, respectively). This study provided an effective approach for promoting the output and durability of TENGs. Meanwhile, this work offers a reliable solution for the development of self-powered sensor networks for smart agriculture.

Effect of Xanthoceras sorbifolium bunge leaves saponins on the foaming properties of whey protein isolate at varying pHs: Correlation between interface, rheology, and foaming characteristics

The interaction between whey protein isolate (WPI) and saponins plays a key role in regulating and improving foam properties. In this study, the influences of Xanthoceras sorbifolium Bunge leaves saponins (XLS) on the foaming properties of WPI were characterized. Results revealed that 0.2 or 0.3% XLS could significantly increase the particle size and turbidity, as well as significantly decrease the protein solubility. The spectrum results showed that there was an interaction between WPI and XLS, which caused the change in protein structure and exposed more hydrophobic groups. Importantly, WPI with 0.3% XLS significantly increased the surface hydrophobicity and decreased the surface tension, resulting in better foaming ability and foam stability. Moreover, the rheological determination suggested that WPI with XLS increased both the apparent viscosity and viscoelasticity. The best foaming performance of WPI was achieved with 0.3% XLS at pH 3, along with the formation of the most compact, smallest, and densest bubbles. According to the classification of mixed conditions suggested by principal component analysis and hierarchical clustering analysis, WPI had good scores in the presence of both 0.2% and 0.3% XLS at pH 3, suggesting that XLS is a promising acidic foam additive applied to WPI food foam.

Detailed investigation on the insulation and permeability characteristics of rigid polyurethane foam loaded with micron-sized Turkey feather powder depending on the free volume change

This study brokes new ground to understand the insulation and permeability performances of rigid polyurethane foams (RPUFs) containing the different contents of micron-sized turkey feather powders (TFPs) depending on the free volume change for the first time. The effects of TFPs loading on the RPUFs were investigated by the examination of their structural and chemical features (particle size and ATR-FTIR analyses), free volume property (PALS analysis), insulation features (thermal conductivity and sound absorption tests), permeability performance (air and water vapor permeability tests) and cellular topology (SEM). PALS analysis results revealed that the addition of TFPs into the foams led to the sharp decrease in all free volume parameters since TFPs caused the formation of the disordered cells by occupying the holes in the matrix. Furthermore, both thermal conductivity and acoustic performance of the resulting foams get worse when compared to unfilled RPUF. This results were attributed to the formation of thinner and weaker cells during polymerization, reduction in the amount of CO2 inside the cells, enhancement in the solid-phase level in the matrix due to the increasing of volumetric density. Additionally, the foam samples with high content of TFPs showed considerably lower air and water vapor permeabilities when compared to neat RPUFs due to the dominant hydrophobic character of the keratin and reduction in the degree of vacancies in the matrix. SEM analysis also revealed that TFPs showed good compatibility with RPUF, but the distorted and irregular shaped cellular morphology was obtained at high contents.

Effect of metal coating on physicochemical properties of ceramic foam for flame suppression application

Combustible dust may result in a catastrophic dust explosion with much larger accident consequences than gas explosions. In this study, porous materials are explored as a promising solution for mitigating explosions. This study focussed on the investigation of aluminium powder explosion in the influence of ceramic foam, with and without coating with non-precious nickel nanopowders. The microscopic properties and structural characteristics of the ceramic foam were analyzed using X-ray spectroscopy, X-ray diffractometry, and scanning electron microscopy. The findings revealed that the nickel-coated ceramic foams are non-uniform and almost spherical in shape, with obvious agglomerations of metallic-silica present on the strut structure. Compared to non-coated ceramic, it can be said that nickel-coated ceramic foams demonstrate a significant reduction in maximum overpressure by approximately 10%. This suggests that the interconnected micro-network structure of the nickel-ceramic walls aids in quenching the flame of the aluminium dust explosion and hence, suppressing the overpressure.

Study on the Dual Effects of MgCl2 on the Characteristics of Foams Stabilized by Sodium Dodecyl Sulfate

Study on the Dual Effects of MgCl₂ on the Characteristics of Foams Stabilized by Sodium Dodecyl Sulfate

Preparation and Characteristics of Biomass Gel Foam with High Foaming and Film-Forming Properties for Preventing Coal Spontaneous Combustion

ABSTRACT To overcome the problem of poor biocompatibility of inorganic gel foam, a biomass gel foam was prepared using carboxymethyl chitosan, tannic acid, and ammonium ferric citrate as raw materials. The results indicated that the gel foam exhibited optimal comprehensive performance when the mass concentrations of foaming agent, stabilizer, gelling agent, and crosslinking agent were 0.8, 0.2, 0.9, and 0.6 wt%, respectively. At this point, the foaming multiple was up to 8 and the half-life was 7.79 days. Compared to pure foam, the gel foam demonstrated excellent water retention and film-forming properties. After continuous heating at 80°C for 10 hours, its water retention rate remained as high as 49.34%. The foam film formed after 120 hours of room temperature drying reached a thickness of 1 cm without any liquid separation phenomenon. The gel foam exhibited a good inhibition effect on the spontaneous combustion and oxidation process of coal. The CO inhibition rate reached 67.43% at 100°C, and the cross-point temperature was effectively delayed by 18.2°C. Moreover, the gel foam exhibited excellent burn resistance properties.

Investigation of CO2 sequestration performance and statistical analysis of dye removal efficiency of liquefied hornbeam based carbon foams: Effects of biomass/solvent weight ratio, tar contribution, and chemical activation

The preparation of carbon foams from bio-based polyols was a preferable alternative for the development of new materials from waste resources. The research described the usage of wood processing factory waste for the production of open-cell carbon foams with a high application potential. Bio-based carbon foams were developed by hornbeam tree sawdust, a low-cost and renewable material for dye removal via adsorption and CO2 uptake performance. In this work, the influences of the solvent type, and solvent/biomass weight ratio on the characteristics of carbon foams were investigated in the solvolytic liquefaction process. A chemical activation process with KOH was applied to the foams and this provided high porosity and surface area (up to 1454 m2/g). Carbon foams were found to have comparable compressive strengths; up to 1.080 MPa. As a result of the statistical analysis, according to the variance analysis performed with a confidence level limit of 95%, it was specified that pH had a negative coefficient and was the most significant factor in NH dye removal. According to the experiments carried out within the scope of investigating the usability of carbon foams in the removal of pollutants from gas and liquid systems, HCFTA-3 carbon foam exhibited a maximum removal efficiency of 55.2% for NH dye when pH was 2, and HCFA-3 carbon foam had the highest CO2 holding capacity at 0 °C as measured by 6.53 mmol/g CO2. This study provided an understanding of the sustainable bio-based carbon foams from industrial waste biomass for practical application of green chemistry.

Experimental investigation on the characteristics of XG/GG/HPAM gel foam and prevention of coal spontaneous combustion

Polymer gel foam shows excellent development potential and application prospects in the prevention of coal spontaneous combustion. To reveal the relationship between the characteristics of gel foam and the prevention of coal spontaneous combustion, XG/GG/HPAM gel foam consisting of polymer xanthan gum (XG), guar gum (GG), and polyacrylamide (HPAM) is prepared. The characteristics of gel foam are investigated in terms of microstructure, viscosity, thermal stability, and film-forming. The effects of gel foam on gas products, characteristic temperature, combustion characteristics parameters, and functional groups during coal oxidation are studied. The results show that polymer delays the foam coarsening and improves the foam stability. XG/GG/HPAM gel foam exhibits a slow foam coarsening process, concentrated bubble diameter distribution, shear-thinning behavior, excellent thermal stability, and film-forming properties. Moreover, the inhibition rate of XG/GG/HPAM gel foam on coal is 43.63% higher than that of ordinary foam. XG/GG/HPAM gel foam effectively improves the apparent activation energy of coal, the maximum weight loss rate of the coal is decreased by 7.55%, and the combustibility, combustion stability, and comprehensive combustion index are diminished by 8.50%, 7.64%, and 10.17%, respectively. Simultaneously, XG/GG/HPAM gel foam reduces the oxidation activity of aliphatic hydrocarbons and oxygen-containing functional groups in coal, blocks the chain reaction, and thus inhibits coal spontaneous combustion. The results provide support for achieving efficient fire prevention performance of gel foam.

Thermally insulating carbon nanotubes and copper ferrite based porous polydimethylsiloxane foams for absorption-dominant electromagnetic interference shielding performance

The exponential growth of the electronic and communication industry in the last 50 years raised serious concerns about electromagnetic (EM) pollution. Consequently, suitable composite materials for electromagnetic interference (EMI) shielding have been developed to reduce EM pollution. In the present work, carbon nanotubes (CNT) and copper ferrite (CuFe2O4) nanoparticle-based porous polydimethylsiloxane (PDMS) composite foams were prepared using the baking soda template method. The PDMS foam acts as the 3-dimensional (3D) porous network, CNT gives the required conductive path and magnetic CuFe2O4 provides the necessary magnetic loss, so that the resultant foams achieved high EMI shielding through the absorption mechanism. Without the inclusion of CuFe2O4, the total EMI SE of the PDMS foam is lower than 20 dB, while various contents of the added CuFe2O4 improve the EMI SE up to 32 dB at a thickness of 3 mm. In addition, the thermal insulation properties are also reported and the resultant material shows a moderately low thermal conductivity of 0.046 W m−1 K−1. These characteristics of the composite foam highlight the strong absorption-dominated EMI shielding and thermal insulation performance, allowing it to successfully meet a wide range of applications.

Scientific gastronomy: On the mechanism by which garlic juice and allicin (thio-2-propene-1-sulfinic acid S-allyl ester) stabilize meringues

Garlic juice (GJ) contains allicin, a bioactive that stabilizes egg white (EW) foams without potassium bitartrate (cream-of-tartar), meeting the aim to identify clean-label ingredients that alter foam characteristics. 0.001 wt% allicin in EWs forms stiff foams with the highest overrun (∼800 %) and delayed drainage (60 min). Whipping EW with GJ or allicin changes the disulfide-bridge conformation of the EW foam from 56, 44, and 0% gauche-gauche-gauche (SSg-g-g), trans-gauche-trans (SSt-g-t), and trans-gauche-gauche (SSt-g-g) to 11, 52, and 37%. Raman microspectrometry (RM) found higher relative percentages of SSg–g–g disulfide bonds coincide with rapid foam collapse, while the tyrosine I850/I830 band ratios, a measure of tyrosine surface exposure, remained constant. These changes in spectra illustrate that polypeptide chain displacement and protein unfolding are essential in stabilizing bubble interfaces. Few clean-label functional compounds alter foam stability and functionality, and compounds such as allicin could lead to entirely new culinary techniques and dishes.